1. Field of the Invention
The present invention relates to a viscous fluid type heat generator of the type which includes a housing assembly defining therein a heat generating chamber in which a viscous fluid is subjected to a shearing action by a rotor element rotating within the heat generating chamber to generate heat. The heat generated by the viscous fluid is transmitted to a heat exchanging liquid, typically water, flowing through a heat receiving chamber defined in the housing assembly and the heat received by the heat exchanging liquid is used as a heat generating source incorporated in, e.g., a heating system or a climate control system of an automobile or another vehicle.
2. Description of the Related Art
U.S. Pat. No. 4,993,377 discloses an example of a vehicle heating system in which a viscous fluid type heat generator, driven by a vehicle engine, generates heat by using a viscous fluid generating heat when it is subjected to a shearing action, is incorporated as a subsidiary heat source. The viscous fluid type heat generator of the vehicle heating system of U.S. Pat. No. '377 is arranged in a secondary water circulating system which is separate from a primary water circulating system circulating an engine-cooling water through an engine-radiator. The primary water circulating system including the engine-radiator functions as a primary heat source for the vehicle heating system.
The engine-cooling water of the secondary water circulating system carries heat generated by the viscous fluid type heat generator to a heat conducting device by which the heat is conducted into a passenger compartment of a vehicle. Thus, the viscous fluid type heat generator functions as an auxiliary heat source for the vehicle heating system, and includes a pair of mutually opposing front and rear housings tightly secured together by appropriate tightening members, such as screw bolts, to define an inner heat generating chamber and a heat receiving chamber arranged so as to surround the heat generating chamber. The heat generating chamber is formed as a fluid-tight chamber and is isolated from the heat receiving chamber by partition walls integral with the front and rear housings, and the heat is exchanged between the viscous fluid in the fluid-tight heat generating chamber and the engine-cooling water in the heat receiving chamber through the partition walls of the housings.
The tightly secured front and rear housings rotatably support a drive shaft therein, via a bearing means, and a rotor element is mounted on an end of the drive shaft so that the rotor element is rotated with the drive shaft within the fluid-tight heat generating chamber. The fluid-tight heat generating chamber is supplied with an appropriate amount of viscous fluid, such as a silicone oil, so that the viscous fluid fills gaps between outer surfaces of the rotor element and partition wall surfaces of the heat generating chamber.
The front housing is provided with a water inlet and a water outlet formed therein, and the above-mentioned heat receiving chamber is fluidly connected to the water inlet to introduce the engine-cooling water therefrom, and is further fluidly connected to the water outlet to discharge the engine-cooling water therethrough. Namely, the heat receiving chamber forms a part of the afore-mentioned secondary water circulating system in which a water pump driven by the vehicle engine is arranged so as to constantly circulate the engine-cooling water through the secondary water circulating system.
When the rotational drive source of the vehicle engine is connected to the drive shaft of the viscous fluid type heat generator via a solenoid clutch, the rotor element fixedly mounted on the drive shaft is rotated therewith within the heat generating chamber to apply a shearing action to the viscous fluid (the silicone oil) held between the outer surfaces of the rotor element and the partition wall surfaces of the heat generating chamber, and accordingly, the viscous fluid frictionally generates heat, and the heat is transmitted to the engine-cooling water circulating through the heat receiving chamber via the partition walls of the heat generating chamber. The engine-cooling water carries the heat to the heat conducting device for the viscous fluid type heat generator, so that the heat conducting device conducts the heat into a passenger compartment of the vehicle.
In the described conventional viscous fluid type heat generator, the rotor element rotating with the drive shaft has a radially outer portion having a circumferential speed larger than that of a radially inner portion thereof extending around the axis of rotation of the rotor element. Thus, the radially outer portion of the rotor element can apply a large shearing speed to the viscous fluid compared with the radially inner portion of the rotor element. Therefore, the viscous fluid held in a region surrounding the radially outer portion of the rotor element has a temperature higher than that of the viscous fluid held in a region adjacent to the radially inner portion of the rotor element. Thus, it is easily understood that transmission of heat from the viscous fluid surrounding the radially outer portion of the rotor element to the engine-cooling water in the heat receiving chamber should effectively be achieved to obtain heat from the viscous fluid, which is sufficient for warming the heated object, namely, the passenger compartment of the vehicle.
Nevertheless, in the conventional viscous fluid type heat generator, the heat receiving chamber is designed so as to permit the engine-cooling water to flow from the water inlet to the water outlet without effectively receiving large amount of heat from the viscous fluid in the heat generating chamber. Namely, the partition walls surrounding the heat generating chamber and fluid-tightly separating the heat generating chamber from the heat receiving chamber are not designed so as to permit effective transmission of heat from the viscous fluid in the heat generating chamber to the engine-cooling water circulating through the heat receiving chamber. Thus, the flow of the engine-cooling water in the heat receiving chamber cannot pass through an outer passage-forming region of the heat receiving chamber where the engine-cooling water is able to receive a large amount of heat transmitting from the viscous fluid which is subjected to the high speed shearing action by the radially outer portion of the rotor element. More specifically, since the outer passage-forming region of the heat receiving chamber is occupied by air so as to prevent the engine-cooling water from reaching that region, the outer passage-forming region of the heat receiving chamber is quite useless from the view point of heat transmission.